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<h1>C++ <span class="color_h1">字符串</span></h1>

<div class="tutintro">
<p>C++ 提供了以下两种类型的字符串表示形式：</p>
<ul class="list">
<li>C 风格字符串</li>
<li>C++ 引入的 string 类类型</li>
</ul>
</div>

<h2 class="tutheader">C 风格字符串</h2>
<p>C 风格的字符串起源于 C 语言，并在 C++ 中继续得到支持。字符串实际上是使用 <b>null</b> 字符  <span class="marked">\0</span>  终止的一维字符数组。因此，一个以 null 结尾的字符串，包含了组成字符串的字符。</p>
<p>下面的声明和初始化创建了一个 <strong>RUNOOB</strong> 字符串。由于在数组的末尾存储了空字符，所以字符数组的大小比单词 <strong>RUNOOB</strong> 的字符数多一个。</p>
<pre>
char site[7] = {'R', 'U', 'N', 'O', 'O', 'B', '\0'};
</pre>
<p>依据数组初始化规则，您可以把上面的语句写成以下语句：</p>
<pre>
char site[] = "RUNOOB";
</pre>
<p>以下是 C/C++ 中定义的字符串的内存表示：</p>
<img decoding="async" src="https://www.runoob.com/wp-content/uploads/2014/09/c-strings-2020-12-21.png" alt="C/C++ 中的字符串表示"/>
<p>其实，您不需要把 <strong>null</strong> 字符放在字符串常量的末尾。C++ 编译器会在初始化数组时，自动把 <span class="marked">\0</span> 放在字符串的末尾。让我们尝试输出上面的字符串：</p>

<div class="example">
<h2 class="example">实例</h2>
<div class="example_code">
<div class="hl-main"><span class="hl-prepro">#include</span><span class="hl-prepro"> </span><span class="hl-quotes">&lt;</span><span class="hl-string">iostream</span><span class="hl-quotes">&gt;</span><span class="hl-prepro"></span><span class="hl-code">
 
</span><span class="hl-reserved">using</span><span class="hl-code"> </span><span class="hl-types">namespace</span><span class="hl-code"> </span><span class="hl-identifier">std</span><span class="hl-code">;
 
</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">main</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-brackets">{</span><span class="hl-code">
   </span><span class="hl-types">char</span><span class="hl-code"> </span><span class="hl-identifier">site</span><span class="hl-brackets">[</span><span class="hl-number">7</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-brackets">{</span><span class="hl-code">'</span><span class="hl-identifier">R</span><span class="hl-code">', '</span><span class="hl-identifier">U</span><span class="hl-code">', '</span><span class="hl-identifier">N</span><span class="hl-code">', '</span><span class="hl-identifier">O</span><span class="hl-code">', '</span><span class="hl-identifier">O</span><span class="hl-code">', '</span><span class="hl-identifier">B</span><span class="hl-code">', '\</span><span class="hl-number">0</span><span class="hl-code">'</span><span class="hl-brackets">}</span><span class="hl-code">;
 
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">菜鸟教程: </span><span class="hl-quotes">&quot;</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">site</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-reserved">return</span><span class="hl-code"> </span><span class="hl-number">0</span><span class="hl-code">;
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
菜鸟教程: RUNOOB
</pre>
<p>C++ 中有大量的函数用来操作以 null 结尾的字符串:</p>
<table class="reference">
<tr><th style="width:5%">序号</th><th>函数 &amp; 目的</th></tr>
<tr><td>1</td><td><b>strcpy(s1, s2);</b><br/>复制字符串 s2 到字符串 s1。</td></tr>
<tr><td>2</td><td><b>strcat(s1, s2);</b><br/>连接字符串 s2 到字符串 s1 的末尾。连接字符串也可以用 <span class="marked">+</span> 号，例如:<br/>
<pre>string str1 = "runoob";
string str2 = "google";
string str = str1 + str2;</pre>

</td></tr>
<tr><td>3</td><td><b>strlen(s1);</b><br/>返回字符串 s1 的长度。</td></tr>
<tr><td>4</td><td><b>strcmp(s1, s2);</b><br/>如果 s1 和 s2 是相同的，则返回 0；如果 s1&lt;s2 则返回值小于 0；如果 s1&gt;s2 则返回值大于 0。</td></tr>
<tr><td>5</td><td><b>strchr(s1, ch);</b><br/>返回一个指针，指向字符串 s1 中字符 ch 的第一次出现的位置。</td></tr>
<tr><td>6</td><td><b>strstr(s1, s2);</b><br/>返回一个指针，指向字符串 s1 中字符串 s2 的第一次出现的位置。</td></tr>
</table>
<p>下面的实例使用了上述的一些函数：</p>

<div class="example">
<h2 class="example">实例</h2>
<div class="example_code">
<div class="hl-main"><span class="hl-prepro">#include</span><span class="hl-prepro"> </span><span class="hl-quotes">&lt;</span><span class="hl-string">iostream</span><span class="hl-quotes">&gt;</span><span class="hl-prepro"></span><span class="hl-code">
</span><span class="hl-prepro">#include</span><span class="hl-prepro"> </span><span class="hl-quotes">&lt;</span><span class="hl-string">cstring</span><span class="hl-quotes">&gt;</span><span class="hl-prepro"></span><span class="hl-code">
 
</span><span class="hl-reserved">using</span><span class="hl-code"> </span><span class="hl-types">namespace</span><span class="hl-code"> </span><span class="hl-identifier">std</span><span class="hl-code">;
 
</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">main</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-brackets">{</span><span class="hl-code">
   </span><span class="hl-types">char</span><span class="hl-code"> </span><span class="hl-identifier">str1</span><span class="hl-brackets">[</span><span class="hl-number">13</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-quotes">&quot;</span><span class="hl-string">runoob</span><span class="hl-quotes">&quot;</span><span class="hl-code">;
   </span><span class="hl-types">char</span><span class="hl-code"> </span><span class="hl-identifier">str2</span><span class="hl-brackets">[</span><span class="hl-number">13</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-quotes">&quot;</span><span class="hl-string">google</span><span class="hl-quotes">&quot;</span><span class="hl-code">;
   </span><span class="hl-types">char</span><span class="hl-code"> </span><span class="hl-identifier">str3</span><span class="hl-brackets">[</span><span class="hl-number">13</span><span class="hl-brackets">]</span><span class="hl-code">;
   </span><span class="hl-types">int</span><span class="hl-code">  </span><span class="hl-identifier">len</span><span class="hl-code"> ;
 
   </span><span class="hl-comment">// 复制 str1 到 str3</span><span class="hl-comment"></span><span class="hl-code">
   </span><span class="hl-identifier">strcpy</span><span class="hl-brackets">(</span><span class="hl-code"> </span><span class="hl-identifier">str3</span><span class="hl-code">, </span><span class="hl-identifier">str1</span><span class="hl-brackets">)</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">strcpy( str3, str1) : </span><span class="hl-quotes">&quot;</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">str3</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-comment">// 连接 str1 和 str2</span><span class="hl-comment"></span><span class="hl-code">
   </span><span class="hl-identifier">strcat</span><span class="hl-brackets">(</span><span class="hl-code"> </span><span class="hl-identifier">str1</span><span class="hl-code">, </span><span class="hl-identifier">str2</span><span class="hl-brackets">)</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">strcat( str1, str2): </span><span class="hl-quotes">&quot;</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">str1</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-comment">// 连接后，str1 的总长度</span><span class="hl-comment"></span><span class="hl-code">
   </span><span class="hl-identifier">len</span><span class="hl-code"> = </span><span class="hl-identifier">strlen</span><span class="hl-brackets">(</span><span class="hl-identifier">str1</span><span class="hl-brackets">)</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">strlen(str1) : </span><span class="hl-quotes">&quot;</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">len</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-reserved">return</span><span class="hl-code"> </span><span class="hl-number">0</span><span class="hl-code">;
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
strcpy( str3, str1) : runoob
strcat( str1, str2): runoobgoogle
strlen(str1) : 12
</pre>

<h2 class="tutheader">C++ 中的 String 类</h2>
<p>C++ 标准库提供了 <b>string</b> 类类型，支持上述所有的操作，另外还增加了其他更多的功能。我们将学习 C++ 标准库中的这个类，现在让我们先来看看下面这个实例：</p>
<p>现在您可能还无法透彻地理解这个实例，因为到目前为止我们还没有讨论类和对象。所以现在您可以只是粗略地看下这个实例，等理解了面向对象的概念之后再回头来理解这个实例。</p> 
<div class="example">
<h2 class="example">实例</h2>
<div class="example_code">
<div class="hl-main"><span class="hl-prepro">#include</span><span class="hl-prepro"> </span><span class="hl-quotes">&lt;</span><span class="hl-string">iostream</span><span class="hl-quotes">&gt;</span><span class="hl-prepro"></span><span class="hl-code">
</span><span class="hl-prepro">#include</span><span class="hl-prepro"> </span><span class="hl-quotes">&lt;</span><span class="hl-string">string</span><span class="hl-quotes">&gt;</span><span class="hl-prepro"></span><span class="hl-code">
 
</span><span class="hl-reserved">using</span><span class="hl-code"> </span><span class="hl-types">namespace</span><span class="hl-code"> </span><span class="hl-identifier">std</span><span class="hl-code">;
 
</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">main</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-brackets">)</span><span class="hl-code">
</span><span class="hl-brackets">{</span><span class="hl-code">
   </span><span class="hl-identifier">string</span><span class="hl-code"> </span><span class="hl-identifier">str1</span><span class="hl-code"> = </span><span class="hl-quotes">&quot;</span><span class="hl-string">runoob</span><span class="hl-quotes">&quot;</span><span class="hl-code">;
   </span><span class="hl-identifier">string</span><span class="hl-code"> </span><span class="hl-identifier">str2</span><span class="hl-code"> = </span><span class="hl-quotes">&quot;</span><span class="hl-string">google</span><span class="hl-quotes">&quot;</span><span class="hl-code">;
   </span><span class="hl-identifier">string</span><span class="hl-code"> </span><span class="hl-identifier">str3</span><span class="hl-code">;
   </span><span class="hl-types">int</span><span class="hl-code">  </span><span class="hl-identifier">len</span><span class="hl-code"> ;
 
   </span><span class="hl-comment">// 复制 str1 到 str3</span><span class="hl-comment"></span><span class="hl-code">
   </span><span class="hl-identifier">str3</span><span class="hl-code"> = </span><span class="hl-identifier">str1</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">str3 : </span><span class="hl-quotes">&quot;</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">str3</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-comment">// 连接 str1 和 str2</span><span class="hl-comment"></span><span class="hl-code">
   </span><span class="hl-identifier">str3</span><span class="hl-code"> = </span><span class="hl-identifier">str1</span><span class="hl-code"> + </span><span class="hl-identifier">str2</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">str1 + str2 : </span><span class="hl-quotes">&quot;</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">str3</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-comment">// 连接后，str3 的总长度</span><span class="hl-comment"></span><span class="hl-code">
   </span><span class="hl-identifier">len</span><span class="hl-code"> = </span><span class="hl-identifier">str3</span><span class="hl-code">.</span><span class="hl-identifier">size</span><span class="hl-brackets">(</span><span class="hl-brackets">)</span><span class="hl-code">;
   </span><span class="hl-identifier">cout</span><span class="hl-code"> &lt;&lt; </span><span class="hl-quotes">&quot;</span><span class="hl-string">str3.size() :  </span><span class="hl-quotes">&quot;</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">len</span><span class="hl-code"> &lt;&lt; </span><span class="hl-identifier">endl</span><span class="hl-code">;
 
   </span><span class="hl-reserved">return</span><span class="hl-code"> </span><span class="hl-number">0</span><span class="hl-code">;
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
str3 : runoob
str1 + str2 : runoobgoogle
str3.size() :  12
</pre>			<!-- 其他扩展 -->
						
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<div id="postcomments"  style="display:none;" >
	<ol class="commentlist">
		<li class="comment byuser comment-author-tianqixin even thread-even depth-1" id="comment-16373"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;小马</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;129***2060@qq.com</p></div><div id="runoobvote-id-16373" data-commid = "16373" class="upvotejs"><a class="upvote"></a> <span class="count">298</span></div></div><div class="comt-main" id="div-comment-16373"><p>string类提供了一系列针对字符串的操作，比如：</p>
<ul><li>
1. append()  -- 在字符串的末尾添加字符</li><li>
2. find()  -- 在字符串中查找字符串</li><li>
4. insert() -- 插入字符</li><li>
5. length() -- 返回字符串的长度</li><li>
6. replace() -- 替换字符串</li><li>
7. substr() -- 返回某个子字符串</li><li>
8. ...</li></ul>

<p>下面是关于string类的实例：</p>

<pre>
#include &lt;iostream&gt;
#include &lt;string&gt;
using namespace std;

int main()
{
    //定义一个string类对象
    string http = "www.runoob.com";

   //打印字符串长度
   cout&lt;&lt;http.length()&lt;&lt;endl;

    //拼接
    http.append("/C++");
    cout&lt;&lt;http&lt;&lt;endl; //打印结果为：www.runoob.com/C++

    //删除
    int pos = http.find("/C++"); //查找"C++"在字符串中的位置
    cout&lt;&lt;pos&lt;&lt;endl;
    http.replace(pos, 4, "");   //从位置pos开始，之后的4个字符替换为空，即删除
    cout&lt;&lt;http&lt;&lt;endl;

    //找子串runoob
    int first = http.find_first_of("."); //从头开始寻找字符'.'的位置
    int last = http.find_last_of(".");   //从尾开始寻找字符'.'的位置
    cout&lt;&lt;http.substr(first+1, last-first-1)&lt;&lt;endl; //提取"runoob"子串并打印

    return 0;
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">小马</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;小马</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;129***2060@qq.com</p></div></span>6年前 (2017-08-15)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-22267"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;自娱、自乐</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;183***3822@qq.com</p></div><div id="runoobvote-id-22267" data-commid = "22267" class="upvotejs"><a class="upvote"></a> <span class="count">66</span></div></div><div class="comt-main" id="div-comment-22267"><p>C++ 中输入的方式其实还有很多，下面来介绍一种与 C 语言中 getchar() 类似的。</p>

<pre>cin.getline();</pre>

<p><strong>cin.getline()</strong> 是在输入一段字符完成后开始读取数据（注意，是输入完成后，以Enter为结束标志）</p>

<p>下面是一实例：输入一串字符，编程统计其中的数字个数和英文字母个数。输入的字符以 <strong>#</strong> 为结束标志。</p>

<pre>#include&lt;iostream&gt;
using namespace std;

#define N 100
int main()
{
    char X[N];
    cin.getline(X,N);                               //以cin.getline形式输入
    int a=0,b=0;
    for(int i=0;i&lt;N;i++)
    {
        if(X[i]=='#')                                      //为#为结束标志
            break;
        if(X[i]&gt;='0'&amp;&amp;X[i]&lt;='9')
            a++;                                         //统计数字个数
        if((X[i]&gt;='a'&amp;&amp;X[i]&lt;='z')||(X[i]&gt;='A'&amp;&amp;X[i]&lt;='Z'))
            b++;                                      //统计英文字母个数
    }
    cout&lt;&lt;a&lt;&lt;endl&lt;&lt;b&lt;&lt;endl;
    return 0;
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">自娱、自乐</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;自娱、自乐</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;183***3822@qq.com</p></div></span>5年前 (2017-12-28)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-22996"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;lhshengshi</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;510***747@qq.com</p></div><div id="runoobvote-id-22996" data-commid = "22996" class="upvotejs"><a class="upvote"></a> <span class="count">66</span></div></div><div class="comt-main" id="div-comment-22996"><p><strong>字符串与vector</strong></p>

<p>字符串字面值与标准库string不是同一种类型</p>

<pre>string s("hello");
cout&lt;&lt;s.size()&lt;&lt;endl;        //OK
cout&lt;&lt;"hello".size()&lt;&lt;endl;  //ERROR
cout&lt;&lt;s+"world"&lt;&lt;endl;       //OK
cout&lt;&lt;"hello"+"world"&lt;&lt;endl; //ERROR</pre>
 

<p>strlen、sizeof与size()求字符串长度的区别</p>

<pre>cout&lt;&lt;strlen("123")&lt;&lt;endl;   //返回 3
cout&lt;&lt;sizeof("123")&lt;&lt;endl;   //返回 4
string s = "123";
cout&lt;&lt;s.size()&lt;&lt;endl;        //返回 3</pre>
 

<p>标准string库中的getline函数返回时会丢弃换行符const iterator与const_iterator的区别</p>

<pre>vector&lt;int&gt;::const_iterator //不能改变指向的值，自身的值可以改变
const vector&lt;int&gt;::iterator //可以改变指向的值，自身的值不能改变
const vector&lt;int&gt;::const_iterator //自身的值和指向的值都是只读的</pre>
<p>任何改变vector长度的操作都会使已存在的迭代器失效。如：在调用push_back之后，就不能再信赖指向vector的迭代器了</p>

<pre>vector&lt;int&gt; ivec;
ivec.push_back(10);
vector&lt;int&gt;::iterator it = ivec.begin();
cout&lt;&lt;*it&lt;&lt;endl;
ivec.push_back(9);
cout&lt;&lt;*it&lt;&lt;endl;      //迭代器已经失效</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">lhshengshi</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;lhshengshi</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;510***747@qq.com</p></div></span>5年前 (2018-01-12)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-27755"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;WOWTOT</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;573***580@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://www.cnblogs.com/luori719/p/5218163.html">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-27755" data-commid = "27755" class="upvotejs"><a class="upvote"></a> <span class="count">114</span></div></div><div class="comt-main" id="div-comment-27755"><p data-title="C++ sizeof 与 strlen的区别">之前一直搞不清 sizeof 和 strlen 到底该怎么区分，最近查了资料：</p>

<p>1、sizeof 操作符的结果类型是 size_t，它在头文件中 typedef 为 unsigned int 类型。该类型保证能容纳实现所建立的最大对象的字节大小。 </p>
<p>2、sizeof 是运算符，strlen 是函数。 </p>
<p>3、sizeof 可以用类型做参数，<strong>strlen</strong> 只能用 <strong>char*</strong> 做参数，且必须是以 <span class="marked">\0</span> 结尾的。</p>
<p>sizeof 还可以用函数做参数，比如： </p>
<pre>short f();
printf("%d\n", sizeof(f()));</pre>
<p>输出的结果是 sizeof(short)，即 2。</p>
<p>4、数组做 <strong>sizeof</strong> 的参数不退化，传递给 <strong>strlen</strong> 就退化为指针了。 </p>

<p>5、大部分编译程序在编译的时候就把 <strong>sizeof</strong> 计算过了，是类型或是变量的长度，这就是 <strong>sizeof(x)</strong> 可以用来定义数组维数的原因。 </p>
<pre>char str[20]="0123456789";
int a=strlen(str); // a=10;
int b=sizeof(str); // 而 b=20;</pre>

<p>6、strlen 的结果要在运行的时候才能计算出来，是用来计算字符串的长度，不是类型占内存的大小。</p>

 
<p>7、sizeof 后如果是类型必须加括弧，如果是变量名可以不加括弧。这是因为 <strong>sizeof</strong> 是个操作符不是个函数。</p>

 

<p>8、当适用一个结构类型或变量时， sizeof 返回实际的大小；当适用一静态地空间数组， sizeof 归还全部数组的尺寸；sizeof 操作符不能返回动态地被分派了的数组或外部的数组的尺寸。</p>


<p>数组作为参数传给函数时传的是指针而不是数组，传递的是数组的首地址， 如： </p>
<pre>fun(char [8])
fun(char [])</pre>
<p>都等价于</p>
<pre>fun(char *) </pre>
<p>在 C++ 里参数传递数组永远都是传递指向数组首元素的指针，编译器不知道数组的大小。</p>
<p>如果想在函数内知道数组的大小， 需要这样做：</p>
<p>进入函数后用memcpy拷贝出来，长度由另一个形参传进去 </p>
<pre>fun(unsiged char *p1, int len)
{
    unsigned char* buf = new unsigned char[len+1]
    memcpy(buf, p1, len);
}</pre>

<p>看了上面的详细解释，发现两者的使用还是有区别的，从这个例子可以看得很清楚：</p>
<pre>char str[20]="0123456789";
int a=strlen(str);         // a=10; &gt;&gt;&gt;&gt; strlen 计算字符串的长度，以结束符 0x00 为字符串结束。
int b=sizeof(str);         // 而 b=20; &gt;&gt;&gt;&gt; sizeof 计算的则是分配的数组 str[20] 所占的内存空间的大小，不受里面存储的内容改变。  </pre>

<p>上面是对静态数组处理的结果，如果是对指针，结果就不一样了。</p>
<pre>char* ss = "0123456789";
sizeof(ss) 结果 4 ＝＝＝》ss 是指向字符串常量的字符指针，sizeof 获得的是一个指针的之所占的空间,应该是长整型的，所以是 4。
sizeof(*ss) 结果 1 ＝＝＝》*ss 是第一个字符 其实就是获得了字符串的第一位 '0' 所占的内存空间，是 char 类型的，占了 1 位
strlen(ss)= 10      ＝＝＝》 如果要获得这个字符串的长度，则一定要使用 strlen。strlen 用来求字符串的长度；而 sizeof 是用来求指定变量或者变量类型等所占内存大小。</pre>

<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/27755">WOWTOT</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;WOWTOT</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;573***580@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://www.cnblogs.com/luori719/p/5218163.html">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2018-05-25)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-29065"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;dx_djh</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;a14***40357@163.com</p></div><div id="runoobvote-id-29065" data-commid = "29065" class="upvotejs"><a class="upvote"></a> <span class="count">61</span></div></div><div class="comt-main" id="div-comment-29065"><p data-title="C++ 字符数组可以用 cout 输出，其他的不行">关于字符数组为什么可以以数组名来用cout输出数组内容，而普通数组不行。</p>

<p>先上范例：</p>

<pre>int a[10] = {1,2,3,6,7};
char b[6] = {'h','a','p','p','y','\0'};
char c[] = "happy";
cout&lt;&lt;a&lt;&lt;endl;
cout&lt;&lt;b&lt;&lt;endl;
cout&lt;&lt;c&lt;&lt;endl;</pre>
<p>输出结果为:</p>

<pre>0x22fe6c
happy
happy</pre>
<p>从以上范例可以看出，普通数组中以数组名用cout来输出，只会得到一串地址；用字符数组则会输出数组中的内容。</p>

<p><strong>那为什么会这样呢？</strong></p>

<p><strong>答案：</strong>因为 <strong>char</strong> 型数组中的每一个元素都是一字节，所以每一个字符之间的地址都是 +1 的是连续的，所以当 cout 输出时读到字符数组中的 <span class="marked">\0</span> 便停止输出; 而 int 数组每个元素占 4 个字节所以数个数组中每个元素地址的间隔是 4，但其实它也是连续的，出现乱码是因没找到结束符。</p>

<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/29065">dx_djh</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;dx_djh</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;a14***40357@163.com</p></div></span>5年前 (2018-07-03)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-40176"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;戒空</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;116***0329@qq.com</p></div><div id="runoobvote-id-40176" data-commid = "40176" class="upvotejs"><a class="upvote"></a> <span class="count">24</span></div></div><div class="comt-main" id="div-comment-40176"><p>Vs2017 使用 strcpy 的时候会报错，提示 strcpy 是不安全的，需要用 strcpy_s 代替。</p>
<pre>#include "pch.h"
#include &lt;iostream&gt;
#include &lt;cstring&gt;

using namespace std;

int main()
{
    char str1[11] = "hello";
    char str2[12] = "world";
    char str3[11];
    int len;


    //复制str1到str2
    strcpy_s(str3, str1);
    cout &lt;&lt; "strcpy(str3, str1):" &lt;&lt; str3 &lt;&lt; endl;

    return 0;
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">戒空</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;戒空</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;116***0329@qq.com</p></div></span>4年前 (2019-02-27)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-42409"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;maxven</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;max***@qq.com</p></div><div id="runoobvote-id-42409" data-commid = "42409" class="upvotejs"><a class="upvote"></a> <span class="count">14</span></div></div><div class="comt-main" id="div-comment-42409"><p><strong data-title>&lt;cstring&gt; 创建详解</strong></p>

<pre>#include&lt;iostream&gt;
#include&lt;algorithm&gt;
#include&lt;cmath&gt;
#include&lt;cstring&gt;
#include&lt;cstdio&gt;
using namespace std;
int main()
{

    //1. 字符串的创建
    cout&lt;&lt;"第一:字符串的创建!\n\n";
    string a(4,'a');
    cout&lt;&lt;"1.以 a 为原字符 4单位大小\n\n";
    cout&lt;&lt;"string a(4,'a');\ncout&lt;&lt;a&lt;&lt;endl;\n";
    cout&lt;&lt;a&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"2.任意大小的字符串\n\n";
    cout&lt;&lt;"string b(\"bbbbbb\");\ncout&lt;&lt;b&lt;&lt;endl;\n";
    string b("bbbbbb");
    cout&lt;&lt;b&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"3.把某一字符串的某一部分\n(0位置开始4个长度)给c\n\n";
    cout&lt;&lt;"string c(a,0,4) ;\ncout&lt;&lt;c&lt;&lt;endl;\n";
    string c(a,0,4) ;
    cout&lt;&lt;c&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"4. 10长度原长度不足补*;\n\n";
    cout&lt;&lt;"c.resize(10,'*');\ncout&lt;&lt;c&lt;&lt;endl;\n";
    c.resize(10,'*');
    cout&lt;&lt;c&lt;&lt;endl&lt;&lt;endl;

    system("pause");
    system("cls");
    return 0;
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/42409">maxven</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;maxven</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;max***@qq.com</p></div></span>4年前 (2019-05-03)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-42410"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;maxven</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;max***@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://过几天会发在%20maxven的博客园">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-42410" data-commid = "42410" class="upvotejs"><a class="upvote"></a> <span class="count">12</span></div></div><div class="comt-main" id="div-comment-42410"><p data-title="&lt;cstring&gt; assign、copy 详解">&lt;cstring&gt; assign() 、 copy() 详解:</p>
<pre>
#include&lt;iostream&gt;
#include&lt;algorithm&gt;
#include&lt;cmath&gt;
#include&lt;cstring&gt;
#include&lt;cstdio&gt;
using namespace std;
int main()
{

    cout&lt;&lt;"第二: 字符串的赋值 assign();"&lt;&lt;endl;
    cout&lt;&lt;"1.感觉就像是append不过是抹除-覆盖\n";
    cout&lt;&lt;"string e;\nchar f[10]=\"123456\"\ne.assign(f);\ne+=' ';\ncout&lt;&lt;e&lt;&lt;endl&lt;&lt;endl;\n";
    string e;
    char f[10]="123456";
    e.assign(f);
    e+=' ';
    cout&lt;&lt;e&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"2.string区间 赋值都类似吧\n";
    cout&lt;&lt;"e.assign(f,3,3);\ne+=' ';\ncout&lt;&lt;e&lt;&lt;endl&lt;&lt;endl;\ne.assign(f,3);\ncout&lt;&lt;e&lt;&lt;endl;\n";
    e.assign(f,3,3);
    e+=' ';
    cout&lt;&lt;e&lt;&lt;endl;
    e.assign(f,3);
    cout&lt;&lt;e&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"3.某字符串char型 全部\n";
    cout&lt;&lt;"char ssr[10]=\"asdqwezxc\";\ne.assign(ssr);\ncout&lt;&lt;ssr&lt;&lt;endl;\n";
    char ssr[10]="asdqwezxc";
    e.assign(ssr);
    cout&lt;&lt;ssr&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"4.某字符串char型 前num个\n";
    cout&lt;&lt;"e.assign(ssr,4);\ncout&lt;&lt;e&lt;&lt;endl;\n";
    e.assign(ssr,4);
    cout&lt;&lt;e&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"5.某字符赋值\n";
    cout&lt;&lt;"赋值3个6\n";
    e.assign(3,'6');
    cout&lt;&lt;e&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"copy() 将d中的2位置开始的12个字符覆盖到char型数组ss上\n 必须为-&gt; char型 &lt;-否则报错";
    cout&lt;&lt;" char ss[10]=\"123\";\n string dd;\nd.copy(ss,12,2);\ncout&lt;&lt;ss&lt;&lt;endl;\n";
    char ss[15]="123";
    string dd("abcdefghijklmn");
    dd.copy(ss,12,2);
    cout&lt;&lt;ss&lt;&lt;endl&lt;&lt;endl;

    system("pause");
    system("cls");
        return 0;
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/42410">maxven</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;maxven</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;max***@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://过几天会发在%20maxven的博客园">&nbsp;&nbsp;参考地址</a></p></div></span>4年前 (2019-05-03)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-42411"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;maxven</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;max***@qq.com</p></div><div id="runoobvote-id-42411" data-commid = "42411" class="upvotejs"><a class="upvote"></a> <span class="count">9</span></div></div><div class="comt-main" id="div-comment-42411"><p data-title="&lt;cstring&gt; append() 详解">&lt;cstring&gt; append() 详解及其扩展(int, char):</p>



<pre>#include&lt;iostream&gt;
#include&lt;algorithm&gt;
#include&lt;cmath&gt;
#include&lt;cstring&gt;
#include&lt;cstdio&gt;
using namespace std;
int main()
{   cout&lt;&lt;"第三: 字符串的添加与复制 append();\nstring d(a);\ncout&lt;&lt;d&lt;&lt;endl;\n//或者 d=d+a;/nd.append(b);\n";

    cout&lt;&lt;"1.在d的末尾添加字符串a\n\n";
    string d(a);
    d.append(b);
    cout&lt;&lt;d&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"2.在d的末尾添加字符串/nb(0位置开始,2个长度)的数据\n\n";
    cout&lt;&lt;"d.append(b,0,2);\ncout&lt;&lt;d&lt;&lt;endl;\n";
    d.append(b,0,2);
    cout&lt;&lt;d&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"3.添加4个 ~ 字符\n\n";
    cout&lt;&lt;"d.append(4,'~');\n";
    cout&lt;&lt;"cout&lt;&lt;d&lt;&lt;endl&lt;&lt;endl;\n";
    d.append(4,'~') ;
    cout&lt;&lt;d&lt;&lt;endl&lt;&lt;endl;

    system("pause");
    system("cls");

    cout&lt;&lt;"4. int 与 char 型添加 (好高兴自己想到的int ^_^ )\n";
    cout&lt;&lt;"char app[100]=\"aaabbb\";";
    cout&lt;&lt;"\nstring charr(\"-_-\");\n";
    cout&lt;&lt;"charr.append(app);\ncout&lt;&lt;charr&lt;&lt;endl\n";
    char app[100]="aaabbb";
    string charr("-_- ");
    charr.append(app);
    cout&lt;&lt;charr&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"charr.append(app,4);\ncout&lt;&lt;charr&lt;&lt;endl&lt;&lt;endl;\n";
    charr.append(app,4);
    cout&lt;&lt;charr&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"char型数组全部,char型数组的前4个\n\n****如果要添加中间***\n";
    cout&lt;&lt;"string tmp;\nstring tmp;tmp.assign(app);\ncharr.assign(\"\");\ncharr.append(tmp,1,4);\ncout&lt;&lt;charr&lt;&lt;endl&lt;&lt;endl;\n";
    string tmp;
    tmp.assign(app);
    charr.assign("");
    charr.append(tmp,1,4);
    cout&lt;&lt;charr&lt;&lt;endl&lt;&lt;endl;

    cout&lt;&lt;"5.int  double 等等 通过 sprintf() &lt;cstdio&gt;作为转接\n";
    cout&lt;&lt;"int aaa=15314;\ndouble bbb=3.1415;\nchar aa[10];\nsprintf(aa,\"%d\",aaa);\ncharr.append(aa,0,4);\nsprintf(aa,\"%f\",bbb);\ncharr.append(aa,0,4);\ncout&lt;&lt;charr&lt;&lt;endl;\n";
    int aaa=15314;
    double bbb=3.1415;
    char aa[10];
    sprintf(aa,"%d",aaa);
    charr.append(aa,0,4);
    sprintf(aa,"%f",bbb);
    charr.append(aa,0,4);
    cout&lt;&lt;charr&lt;&lt;endl&lt;&lt;endl;

    system("pause");
    system("cls");
    return 0;
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/42411">maxven</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;maxven</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;max***@qq.com</p></div></span>4年前 (2019-05-03)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-50168"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;阳平</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;yua***ongtt@163.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://blog.csdn.net/u011486738/article/details/82082405">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-50168" data-commid = "50168" class="upvotejs"><a class="upvote"></a> <span class="count">108</span></div></div><div class="comt-main" id="div-comment-50168"><p data-title="C++ 中常见的几种输入字符串的方法"><strong>C++ 中常见的几种输入字符串的方法如下：</strong></p>

<p>cin、cin.get()、cin.getline()、getline()、gets()、getchar()</p>

<h3>1. cin&gt;&gt;</h3>

<p>用法一：最常用、最基本的用法，输入一个数字：</p>

<pre>#include &lt;iostream&gt;
using namespace std;
int main ()
{
  int a,b;
  cin&gt;&gt;a&gt;&gt;b;
  cout&lt;&lt;a+b&lt;&lt;endl;
}

//输入：2[回车]3[回车]
//输出：5
​</pre>
<p>用法二：接受一个字符串，遇“空格”、“Tab”、“回车”都结束</p>

<pre>#include &lt;iostream&gt;
using namespace std;
int main ()
{
  char a[20];
  cin&gt;&gt;a;
  cout&lt;&lt;a&lt;&lt;endl;
}
​
//输入：jkljkljkl
//输出：jkljkljkl
​
//输入：jkljkl jkljkl //遇空格结束，所以不能输入多个单词
//输出：jkljkl</pre>
<h3>2. cin.get()</h3>

<p>用法一：cin.get(字符变量名)可以用来接收字符</p>

<pre>#include &lt;iostream&gt;
using namespace std;
int main ()
{
char ch;
ch=cin.get(); //或者cin.get(ch);只能获取一个字符
cout&lt;&lt;ch&lt;&lt;endl;
}
​
//输入：jljkljkl
//输出：j</pre>
<p>用法二：cin.get(字符数组名，接收字符数)用来接收一行字符串，可以接收空格</p>

<pre>#include &lt;iostream&gt;
using namespace std;
int main ()
{
char a[20];
cin.get(a,20); //有些类似getline。可以输入多个单词，中间空格隔开。
cout&lt;&lt;a&lt;&lt;endl;
}
​
//输入：jkl jkl jkl
//输出：jkl jkl jkl
​
//输入：abcdeabcdeabcdeabcdeabcde （输入25个字符）
//输出：abcdeabcdeabcdeabcd （接收19个字符+1个'\0'）
​</pre>
​
<p>用法三：cin.get(无参数)没有参数主要是用于舍弃输入流中的不需要的字符, 或者舍弃回车, 弥补cin.get(字符数组名,接收字符数目)的不足.</p>

<pre>#include &lt;iostream&gt;
using namespace std;
 
int main(void)
{
     
    char arr[10];
    cin.get(arr,10);
    cin.get();//用于吃掉回车，相当于getchar();
    cout&lt;&lt;arr&lt;&lt;endl;
    cin.get(arr,5);
    cout&lt;&lt;arr&lt;&lt;endl;
    system("pause");
    return 0;
}
 
//输入abcdefghi
//输出abcdefghi
//输入abcde
//输出abcd
//请按任意键继续</pre>
 
<pre>#include &lt;iostream&gt;
using namespace std;
 
int main(void)
{
     
    char arr[10];
    cin.get(arr,10);
    //cin.get();//用于吃掉回车，相当于getchar(); 现在把这行注释掉试试看
    cout&lt;&lt;arr&lt;&lt;endl;
    cin.get(arr,5);
    cout&lt;&lt;arr&lt;&lt;endl;
    system("pause");
    return 0;
}
 
//输入abcdefghi
//输出abcdefghi
//请按任意键继续</pre>
<h3>3.cin.getline()</h3>

<p>cin.getline(): 接受一个字符串，可以接收空格并输出</p>

<pre>#include &lt;iostream&gt;
using namespace std;
int main ()
{
char m[20];
cin.getline(m,5); //与上面基本相同。
cout&lt;&lt;m&lt;&lt;endl;
}
​
//输入：jkljkljkl
//输出：jklj</pre>
<p>接受5个字符到m中，其中最后一个为'\0'，所以只看到4个字符输出；
​</p>
<p>如果把5改成20：</p>
<pre>输入：jkljkljkl
输出：jkljkljkl
​
输入：jklf fjlsjf fjsdklf
输出：jklf fjlsjf fjsdklf</pre>
<p>延伸：</p>
<p>cin.getline()实际上有三个参数，cin.getline(接受字符串到m,接受个数5,结束字符)</p>
<p>当第三个参数省略时，系统默认为'\0' 是‘/n’吧。</p>
<p>如果将例子中cin.getline()改为cin.getline(m,5,'a');当输入jlkjkljkl时输出jklj，输入jkaljkljkl时，输出jk</p>
<p>当用在多维数组中的时候，也可以用cin.getline(m[i],20)之类的用法：
​</p>
<pre>#include&lt;iostream&gt;
#include&lt;string&gt;
using namespace std;
​
int main ()
{
char m[3][20];
for(int i=0;i&lt;3;i++)
{
cout&lt;&lt;"\n请输入第"&lt;&lt;i+1&lt;&lt;"个字符串："&lt;&lt;endl;
cin.getline(m[i],20);
}
​
cout&lt;&lt;endl;
for(int j=0;j&lt;3;j++)
cout&lt;&lt;"输出m["&lt;&lt;j&lt;&lt;"]的值:"&lt;&lt;m[j]&lt;&lt;endl;
​
}</pre>
​<p>测试：</p>
<pre>请输入第1个字符串：
kskr1
​
请输入第2个字符串：
kskr2
​
请输入第3个字符串：
kskr3
​
输出m[0]的值:kskr1
输出m[1]的值:kskr2
输出m[2]的值:kskr3</pre>
​
<h3>4. getline()</h3>

<p>getline() ：接受一个字符串，可以接收空格并输出，需包含 <span class="marked">#include&lt;string&gt;</span>。 </p>

<pre>#include&lt;iostream&gt;
#include&lt;string&gt;
using namespace std;
int main ()
{
    string str;
    getline(cin,str);
    cout&lt;&lt;str&lt;&lt;endl;
}
​</pre>
<p>测试：</p>
<pre>输入：jkljkljkl //VC6中有个bug,需要输入两次回车。
输出：jkljkljkl
​
输入：jkl jfksldfj jklsjfl
输出：jkl jfksldfj jklsjfl</pre>
​
<p>和cin.getline()类似，但是cin.getline()属于istream流，而getline()属于string流，是不一样的两个函数</p>
<h3>5. gets()</h3>
<p>
gets()： 接受一个字符串，可以接收空格并输出，需包含 <span class="marked">#include&lt;string&gt;</span>。</p>

<pre>#include&lt;iostream&gt;
#include&lt;string&gt;
using namespace std;
int main ()
{
    char m[20];
    gets(m); //不能写成m=gets();
    cout&lt;&lt;m&lt;&lt;endl;
}</pre>
<p>​测试：</p>
<pre>输入：jkljkljkl
输出：jkljkljkl
​
输入：jkl jkl jkl
输出：jkl jkl jkl</pre>
​
<p>类似cin.getline()里面的一个例子，gets()同样可以用在多维数组里面：
​</p>
<pre>#include&lt;iostream&gt;
#include&lt;string&gt;
using namespace std;
​
int main ()
{
    char m[3][20];
    for(int i=0;i&lt;3;i++)
    {
        cout&lt;&lt;"\n请输入第"&lt;&lt;i+1&lt;&lt;"个字符串："&lt;&lt;endl;
        gets(m[i]);
    }
​
    cout&lt;&lt;endl;
    for(int j=0;j&lt;3;j++)
        cout&lt;&lt;"输出m["&lt;&lt;j&lt;&lt;"]的值:"&lt;&lt;m[j]&lt;&lt;endl;
}</pre>
<p>​测试：</p>
<pre>请输入第1个字符串：
kskr1
​
请输入第2个字符串：
kskr2
​
请输入第3个字符串：
kskr3
​
输出m[0]的值:kskr1
输出m[1]的值:kskr2
输出m[2]的值:kskr3</pre>
​
<p>自我感觉gets()和cin.getline()的用法很类似，只不过cin.getline()多一个参数罢了；
​</p>
<p>这里顺带说明一下，对于本文中的这个kskr1,kskr2,kskr3的例子，对于cin>>也可以适用，原因是这里输入的没有空格，如果输入了空格，比如“ks kr jkl[回车]”那么cin就会已经接收到3个字符串，“ks,kr,jkl”；再如“kskr 1[回车]kskr 2[回车]”，那么则接收“kskr,1,kskr”；这不是我们所要的结果！而cin.getline()和gets()因为可以接收空格，所以不会产生这个错误；</p>
<h3>6.getchar()</h3>

<p>getchar() ：接受一个字符，需包含 <span class="marked">#include&lt;string&gt;</span>。</p>


<pre>#include&lt;iostream&gt;
using namespace std;
int main ()
{
    char ch;
    ch=getchar(); //不能写成getchar(ch);
    cout&lt;&lt;ch&lt;&lt;endl;
}
​</pre>
<p>测试：</p>
<pre>输入：jkljkljkl
输出：j</pre>
​
<p>getchar()是C语言的函数，C++也可以兼容，但是尽量不用或少用；</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/50168">阳平</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;阳平</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;yua***ongtt@163.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://blog.csdn.net/u011486738/article/details/82082405">&nbsp;&nbsp;参考地址</a></p></div></span>3年前 (2020-01-18)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-51237"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;周大侠</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;277***091@qq.com</p></div><div id="runoobvote-id-51237" data-commid = "51237" class="upvotejs"><a class="upvote"></a> <span class="count">46</span></div></div><div class="comt-main" id="div-comment-51237"><p><a href="#div-comment-29065" rel="nofollow ugc"><span class="marked">@dx_djh</span></a></p><p>关于整形数组的解释是错误的，即使整形数组加上结束符，cout输出的也是地址，这是c++的机制。只有数组是char类型时，cout数组名才会输出内容，其他类型的都会输出地址。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">周大侠</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;周大侠</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;277***091@qq.com</p></div></span>3年前 (2020-03-05)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-52862"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;秋叶</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;251***7981@qq.com</p></div><div id="runoobvote-id-52862" data-commid = "52862" class="upvotejs"><a class="upvote"></a> <span class="count">18</span></div></div><div class="comt-main" id="div-comment-52862"><p><strong>原始字符串(C++11)</strong></p>

<strong>R"(字符串)"</strong> 为默认格式的原始字符串，原始字符串内的字符不进行转义。

<pre>#include&lt;iostream&gt;
using namespace std;
int main ()
{
    cout &lt;&lt; R"(原始\t字\n符串)" &lt;&lt; endl;
    return 0;
}</pre>
​
<p>输出: </p><pre>原始\t字\n符串</pre>
<p><strong>自定义分隔符</strong></p>
<p>
分隔符可支持自定义，写在括号外部，左右需要一致，不是所有的字符都可以设置为分隔符：</p>

<pre>#include&lt;iostream&gt;
using namespace std;
int main ()
{
    cout &lt;&lt; R"#%^&amp;*(1231)"123)#%^&amp;*" &lt;&lt; endl;
    return 0;
}</pre>
<p>输出:</p> <pre>1231)"123</pre>
<p>字符串前缀：</p>

<pre>L : 类型 wchar_t      编码 : Unicode
u : 类型: char16_t    编码 : UTF-16  (C++11)
U : 类型: char32_t     编码 : UTF-32 (C++11)
u8 : 类型 char          编码 : UTF-8     (C++11)</pre>
<p>实例：</p>
<pre>#include&lt;iostream&gt;
using namespace std;
int main ()
{
    wcout &lt;&lt; L"Unicode 字符串" &lt;&lt; endl; //控制台字符类型为Unicode时，正常输出
    wcout &lt;&lt; u"utf-16 字符串" &lt;&lt; endl;  //wcout 不支持的类型，输出地址
    wcout &lt;&lt; U"utf-32 字符串" &lt;&lt; endl;  //wcout 不支持的类型，输出地址
    cout &lt;&lt; u8"utf-8 字符串" &lt;&lt; endl;   //控制台字符类型为UTF-8时，正常输出
    return 0;
}​</pre><p>
输出:</p>
<pre>Unicode 字符串
00007FF7FB864480
00007FF7FB864498
utf-8 瀛楃涓?</pre>
<p>字符串前缀与原始字符串组合：</p>

<pre>#include&lt;iostream&gt;
using namespace std;
int main ()
{
    wcout &lt;&lt; LR"(\t字\b符\r串\n)" &lt;&lt; endl;
    return 0;
}​</pre>
<p>输出:</p>
<pre>\t字\b符\r串\n</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">秋叶</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;秋叶</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;251***7981@qq.com</p></div></span>3年前 (2020-04-20)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-59666"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Yingfan</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;yin***nzhou@outlook.com</p></div><div id="runoobvote-id-59666" data-commid = "59666" class="upvotejs"><a class="upvote"></a> <span class="count">30</span></div></div><div class="comt-main" id="div-comment-59666"><p>菜鸟教程上有一个没有讲清楚的地方，即关于C风格的字符串中,strcmp(s1, s2)函数的使用，菜鸟教程中是这样描述的</p><p>strcmp(s1, s2);</p><p>如果 s1 和 s2 是相同的，则返回 0；如果 s1&lt;s2 则返回值小于 0；如果 s1&gt;s2 则返回值大于 0。</p><p>然而实际上更准确来说，是如果两个字符串不匹配，且第一个字符串的第一个字符小于第二个字符串的第一个字符，才会返回比0小的值，反之则返回比0大的值。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Yingfan</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Yingfan</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;yin***nzhou@outlook.com</p></div></span>2年前 (2020-12-18)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-71260"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;上帝也代码</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;717***589@qq.com</p></div><div id="runoobvote-id-71260" data-commid = "71260" class="upvotejs"><a class="upvote"></a> <span class="count">12</span></div></div><div class="comt-main" id="div-comment-71260"><p>分享一个 <strong>const char</strong> 数组和 <strong>const char*</strong> 数组以及跟 <strong>int</strong> 数组指针输出案例。</p>

<pre>#include &lt;iostream&gt;
using namespace std;

void main() {
    //const char的变
    const char aa[8] = "abcdefg";
    const char* bb = "1234567";
    cout &lt;&lt; bb &lt;&lt; endl;  //输出1234567
    cout &lt;&lt; *bb &lt;&lt; endl;  //输出1
    cout &lt;&lt; bb+1 &lt;&lt; endl; //输出234567
    cout &lt;&lt; *(bb + 1) &lt;&lt; endl; //输出2
    cout &lt;&lt; (*bb + 2) &lt;&lt; endl; //bb指针地址123456，指向的内容为1，所以*bb='1',1的ASCII为49，所以输出(*bb + 2)=51

    cout &lt;&lt; "--------------" &lt;&lt; endl;
    const char *charp, *charp2;
    cout &lt;&lt; aa&lt;&lt; endl; //输出abcdefg
    cout &lt;&lt; *aa &lt;&lt; endl; //输出a
    charp = aa;  //此时如果调用cout &lt;&lt; charp &lt;&lt; endl;输出abcdefg；调用cout &lt;&lt; *charp &lt;&lt; endl;输出a
    charp=&amp;aa[0];
    charp2= &amp;aa[1];  //charp2为const char*指向aa[1]='b'字符，调用*charp2输出b，但是调用charp2将会输出bcdefg
    cout &lt;&lt; *charp &lt;&lt; endl; //输出字符a
    cout &lt;&lt; charp &lt;&lt; endl; //输出字符串abcdefg
    cout &lt;&lt; *charp2 &lt;&lt; endl;//输出字符b
    cout &lt;&lt; charp2 &lt;&lt; endl; //输出字符串bcdefg

    cout &lt;&lt; "--------------" &lt;&lt; endl;

    int i[5] = { 1,2,3,4,5 };
    int *ip, *ip2;
    ip = i;
    cout &lt;&lt; i &lt;&lt; endl;//输出00CFFE44地址
    cout &lt;&lt; *i &lt;&lt; endl;//输出数值1
    cout &lt;&lt; ip &lt;&lt; endl; //输出00CFFE44地址，地址指向的内容为数值1
    cout &lt;&lt; *ip &lt;&lt; endl; //输出数值1

    system("pause");
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">上帝也代码</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;上帝也代码</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;717***589@qq.com</p></div></span>1年前 (2022-03-22)</div></div></li><!-- #comment-## -->
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